Water pours down on the streets
Headlines such as these are common in our newspapers and on radio
And television. They inform us of the damage and devastation that
Natural hazards inflict on people and the environment. Many of
These natural hazards are made worse by the activities of people.
Each year flooding costs Australia, on average, $300-$400 million.
The majority of deaths from flooding are the result of people trying
To drive, walk or swim through floodwaters. Some are killed while
Camping on dry river beds.
Flash floods can be extremely dangerous. Caused by heavy rainfall
Many kilometres away, flash floodwaters can surge down river
Channels, sweeping away all in their path: they can move boulders,
Tear out trees and destroy buildings and bridges.

A flood can result from prolonged heavy rain, winter snow thaws or
Sudden, heavy downpours. A flood occurs when water overflows its
Natural banks on to normally dry land, such as when a river bursts its
Banks. For example, the 1996 Queensland floods resulted from a
Week of constant heavy rain: nearly 30 centimetres of rain fell in
Twenty-four hours. This caused the Brisbane River to rise 9 metres
During one day, necessitating the evacuation of people from large
Areas of Ipswich and low-lying areas

A flood’s build up can be slow or fast, but usually it develops over
a period of days. Slow-onset floods may last for a week or more-
Even months. These floods can lead to loss of stock, damage to crops
And extensive damage to road and rail links. Rivers in central and
Western New South Wales and Queensland, as well as parts of
Western Australia can flood in this way. Rapid-onset floods occur
More quickly in mountain headwater areas of larger rivers and in
Rivers draining to the coast. These floods may last only one or two
Days. They are potentially more damaging, however, with greater risk
To life and property since there is often less time to take preventive
Action.
Flash floods occur when intense storms drop large amounts of rain
Within a brief period of time. They can occur with little or no
Warning and can reach their peak in only a few minutes. Almost all
Parts of Australia can experience flash floods. These floods pose the
Greatest threat to life and result in significant damage to property.
They are a serious problem in those urban areas where drainage
Systems are unable to cope. In December 2003, the worst storm related
Flash flood in 100 years resulted in extensive flooding.
Human activities in catchments have contributed to a sharp rise in
The incidence and severity of flooding. People increase the
Likelihood of flooding by removing water-absorbing vegetation,
Especially on hillsides. Not only does this increase runoff, it also
Exposes the soil to erosion, especially by running water. Valuable soil
Is washed into rivers, where it clogs the channels. The rivers are
Then less able to cope with the increased volumes of water.
The construction of expensive flood mitigation works, such as
Levee banks, provides some protection but the best solution is to
Restrict the types of activities allowed on flood plains. Too many
People still choose to live in flood-prone areas.
Urban areas, with their hard, impervious surfaces, are often
Affected by flash flooding. Heavy downpours can overwhelm the
Capacity of stormwater drains and cause water to spill across
Roadways and footpaths.